Patent application title: Method and System for Fire Simulation

Abstract:

A fire simulation method and system for simulating ammunition from a
weapon. The method includes determining a trajectory of the simulated
ammunition, emitting a light beam along a simulation axis, and coding
said light beam with information. The method includes determining a point
in time when the simulated ammunition passes a target, determining a
value related to the distance between the simulation axis and a momentary
position of the simulated ammunition along the trajectory at that point
in time, and emitting the light beam coded with the determined value
during a predetermined time period.

Claims:

1. A fire simulation method for simulating ammunition from a weapon, the
method comprising:determining a trajectory of the simulated
ammunition,emitting a light beam along a simulation axis, andcoding said
light beam with information,determining a point in time when the
simulated ammunition passes a target,determining a value related to the
distance between the simulation axis and a momentary position of the
simulated ammunition along the trajectory at that point in time
andemitting the light beam coded with the determined value during a
predetermined time period.

2. The fire simulation method according to claim 1, further
comprising:determining the position of at least one potential target
object, and directing the emitted light beam toward said target.

3. The fire simulation method according to claim 2, wherein the
determination of the position of at least one target object includes
determining the geographical position of potential target objects within
a target area for the weapon.

4. The fire simulation method according to claim 3, wherein the aiming of
the weapon is sensed and that the sensed aiming and information about the
range of the weapon is used in determining the target area.

5. The fire simulation method according to claim 1, wherein the
determination of the point in time when the simulated ammunition passes
the target object includesdetermining a first distance between the weapon
and each potential target object, andcomparing said first distance to a
second distance to a momentary position of the simulated ammunition along
the trajectory.

6. The fire simulation method according to claim 1, wherein the light beam
is caused to execute a sweeping movement during the predetermined time
period and wherein for each direction of the sweep a new value
corresponding to said direction is determined and coded into the light
beam.

7. A fire simulation system, comprising:a transmitter arranged to emit a
light beam along a simulation axis to simulate ammunition from a
weapon,coding means arranged to code the light beam with
information,processing means arranged to calculate a trajectory of the
simulated ammunition, wherein the processing means further are arranged
to determine a point in time when the simulated ammunition passes a
target object, anda control unit is arranged to activate the transmitter
for a predetermined time period from said point in time, wherein the
control unit is arranged to determine a value related to the distance
between the simulation axis and a momentary position of the simulated
ammunition along the trajectory at the determined point in time and
wherein said coding means are arranged to code said light beam with the
determined value.

8. The fire simulation system according to claim 7, further
comprising:means for determining the position of at least one target
object, andcontrollable steering means arranged to steer the direction of
the simulation axis toward the target.

9. The fire simulation system according to claim 8, wherein the means for
determining the position is arranged to continuously update the
geographical position of the weapon and of potential targets within a
target area for the weapon.

10. The fire simulation system according to claim 9, wherein the weapon is
provided with an orientation sensor arranged to sense the aiming of the
weapon and wherein the target area is determined by at least the aiming
and the range of the weapon.

11. The fire simulation system according to claim 7, wherein the
processing means is arranged to determine a first distance between the
weapon and each potential target object and to continuously compare said
first distance to a second distance to the momentary position of the
ammunition along the trajectory in order to determine the point in time
when the ammunition passes a target object.

12. The fire simulation system according to claim 8, wherein said steering
means are arranged to cause the light beam to execute a sweeping movement
during the predetermined time period and in that the coding means are
arranged to code the light beam for each direction of the sweep with a
value representative of said direction.

13. The fire simulation system according to claim 7, wherein said
transmitter is a laser transmitter arranged so as to transmit laser
radiation with at least one beam lobe.

14. The fire simulation system according to claim 7, wherein the coding
means is arranged to code information in the light beam, which
information identifies the target object.

15. The fire simulation system according to claim 8, wherein the fire
simulation system is disposed at a weapon.

16. A weapon effect simulation system, comprising:a fire simulation system
according to claim 7, andat least one hit simulation system provided on
each target object, said hit simulation system comprisingmeans arranged
to receive the emitted light beam andmeans arranged to determine whether
the corresponding target object has been hit based on the value coded in
the light beam.

17. The weapon effect simulation system according to claim 16, wherein at
least one of the hit simulation systems comprises a transmitter, and
wherein the fire simulation system further comprises a receiver arranged
so as to receive information from the transmitter of the hit simulation
system.

18. The weapon effect simulation system according to claim 17, wherein the
transmitter is arranged so as to transmit a hit message upon
determination of a hit.

19. The weapon effect simulation system according to claim 18, wherein the
control unit is arranged so as to break off the simulation upon reception
of the hit message.

20. The weapon effect simulation system according to claim 16, wherein the
means arranged to determine hit are arranged so as to determine the hit
location on the target.

Description:

TECHNICAL AREA

[0001]The present invention relates to a fire simulation method for
simulating ammunition from a weapon in accordance with the preamble of
claim 1.

[0002]The present invention further relates to a fire simulation system
comprising a transmitter arranged to emit a light beam along a simulation
axis to simulate ammunition from a weapon, coding means arranged to code
the light beam with information, and processing means arranged to
calculate a trajectory of a simulated ammunition. Ammunition refers to
grenades, projectiles, missiles, rockets (i.e. projectiles with rocket
engines), sector charges, etc.

STATE OF THE ART

[0003]When, in the same manner as during actual firing, a weapon is aimed
at a target during fire simulation, it is necessary to determine the
extent to which a live round fired using the alignment that the weapon
has during the simulated firing would or would not hit the target. It is
also desirable to be able to determine the hit location and the effect of
the hit.

[0004]U.S. Pat. No. 4,218,834 describes a weapon simulation method based
on a laser transmitter disposed on or near the weapon. The laser
transmitter is arranged to emit laser radiation in the direction in which
the weapon is pointed, and the targets are equipped with reflectors
arranged so as to reflect the laser radiation back toward the weapon.
Means disposed at the weapon to generate a projectile trajectory signal
are started simultaneous with the firing of a simulated projectile. The
projectile trajectory signal reproduces the continuously changing
position of an imagined real projectile fired at the same moment as the
simulated projectile, and contains a distance value calculated with
reference to the weapon, plus calculated aiming values referenced to a
predetermined axis pointing from the weapon in the direction of the
projectile trajectory.

[0005]The laser radiation is caused to execute a sweeping movement in
order to scan an area in front of the weapon, whereupon the radiation
that is reflected from target reflectors located in front of the weapon
is received. Signals are generated from the received radiation that
contain a distance value based on a measurement of the time between the
transmission and reception of the reflected radiation, which value is
comparable with the calculated distance value, and aiming values
corresponding to the current radiation, which aiming values are
comparable with the calculated aiming values. The measured values are
compared with the comparable calculated values in order to determine
whether the real projectile would have hit the target. Selectivity in
connection with the transmission of information to only one of a
plurality of conceivable targets within the solid angle area swept by the
sweeping movement is achieved in that the information is transmitted only
for as long as reflected radiation is being received from each respective
reflector. Selectivity with respect to receiving information is achieved
in that certain conditions are set in order for received information to
be accepted. Additional selectivity is achieved in that the foregoing
valid information is transmitted only during those sweep periods that
correspond to a correct distance having been attained in the ongoing
projectile trajectory simulation. The foregoing conditions are described
in detail in the weapon simulation method specified in U.S. Pat. No.
4,218,834. U.S. Pat. No. 6,386,879 describes a weapon simulation system
based on similar principles, but here the target is arranged so as to
receive and assess received radiation. This system thus uses no
reflectors. A GPS antenna is disposed in connection with the weapon, via
which antenna position information for the weapon is received. Means for
emitting laser radiation and for including information concerning the
time the projectile was fired, the weapon identity, weapon type,
projectile type, weapon angles of inclination and rotation, the
geographical position and, if applicable, the speed of the weapon are
also present in connection with the weapon. In the target there are means
for detecting the laser radiation in order to determine azimuth and
elevation data for the target, means for determining a range to the
target by comparing the received GPS coordinates for the weapon with the
GPS coordinates for the target as measured by means of a GPS received
disposed in the target, and means for determining a hit location relative
to the target for a ballistic projectile fired from the weapon at the
time of firing as based on determined azimuth and elevation data for the
target plus information included in the laser radiation.

[0006]Thus, simulation according to U.S. Pat. No. 6,386,879 is based on
transmitting complete documentation in the form of the geographical
position, speed and direction of the firing system at the instant of
firing, the alignment of the weapon, etc., to the target after the
instant of firing for subsequent processing in the target system. The
target system itself calculates, based on the provided documentation, a
hit location in relation to the target, including the entire movement of
the target during the flight time of the ammunition. One of the
disadvantages of the system according to U.S. Pat. No. 6,386,879 is that
it does not permit any realistic simulation of ammunition that is guided
by the gunner or observer/forward observer, wherein the trajectory of the
ammunition can be corrected after firing.

DESCRIPTION OF THE INVENTION

[0007]One object of the present invention is to achieve a weapon
simulation system that enables precision simulation of both ballistic and
guided ammunition without the presence of reflectors.

[0008]This has been achieved according to one embodiment of the present
invention by means of a fire simulation method for simulating ammunition
from a weapon comprising the following steps: [0009]determining a
trajectory of the simulated ammunition, [0010]emitting a light beam along
a simulation axis, and [0011]coding said light beam with the information.

[0012]The fire simulation method is characterized by the following steps:
[0013]determining a point in time when the simulated ammunition passes a
target, [0014]determining a value related to the distance between the
simulation axis and a momentary position of the simulated ammunition
along the trajectory at the determined point in time and [0015]emitting
the light beam coded with the determined value during a predetermined
time period.

[0016]The weapon can be a live weapon or a replica of a live weapon. The
weapon can, for instance, be person-borne or vehicle-borne. In yet
another embodiment the weapon is virtual, and its entire existence is
simulated by a fire simulation system at an observer/forward observer, or
a command and control system.

[0018]The step of determining trajectory of the simulated ammunition
includes calculating the trajectory based on ammunition type. For
ammunition with a ballistic trajectory, the azimuth and elevation of the
weapon, the weight of the ammunition and the actual muzzle velocity of
the weapon can be used in known manner to calculate the trajectory. In a
case involving guided ammunition, the gunner or observer/forward observer
can guide the ammunition. For example, the ammunition is guided
continuously using a joystick, whereupon the positional status of the
joystick is continuously used for updating the trajectory of the
simulated ammunition. In an alternative case where the ammunition is
guided toward the target automatically, the determination of the
trajectory includes simulating an auto-seeking function In addition to
the foregoing trajectory parameters (ballistic trajectory, manually
guided trajectory, automatically guided trajectory), which are determined
by the ammunition chosen and the weapon type, the trajectory is based on
one or more predetermined parameters. These predetermined parameters
include, e.g. timing ranges and variable time fuses on/off, which are set
by the gunner, observer or command and control system. The trajectory can
also be determined based on stochastic parameters, such as weather
conditions. Furthermore, e.g. topographical conditions and other terrain
conditions can be allowed to influence the trajectory.

[0019]One advantage with the method is that a light beam simulating
ammunition is only emitted in the same moment as the ammunition passes or
hits a target. Therefore batteries can be saved in the transmitters
emitting the laser beams as the time of emission is substantially
shortened. As the light beam is only emitted when the ammunition passes
the target object, the risk of fighting targets not hit by the ammunition
is practically eliminated. Further, as the emission is only activated
when there is a possibility that a target has been hit, target systems
receiving and evaluating the emitted light beam are less loaded with
information about ammunition that does not affect the target.

[0020]In a preferred embodiment of the invention, the method further
comprises the steps of determining the position of at least one potential
target object, and directing the emitted light beam toward said target.

[0021]The step of determining the position of at least one potential
target object includes in one embodiment determining the geographical
positions of targets within a target area for the weapon. The target area
can be determined by sensing the aiming of the weapon and calculating the
area based on the geographical position of the weapon, the aiming of the
weapon and the range of the weapon. The geographical position of the
weapon and target/targets can be obtained by receiving position from a
satellite based positioning system such as GPS.

[0022]The step of determining a point in time when the simulated
ammunition passes the target includes in one embodiment of the invention
determining a first distance between the weapon and each target object
and comparing said first distance to a second distance to a momentary
position of the simulated ammunition along the trajectory.

[0023]The light beam emitted is for example generated by laser. The laser
can be working in the IR range or another frequency range. In one
embodiment of the invention the emitted light beam is caused to execute a
sweeping movement and for each direction of the sweep a new value related
to the distance between the simulation axis and the momentary position of
the ammunition along the trajectory is calculated and the determined new
value is coded in the light beam.

[0024]The invention also comprises a system comprising a transmitter
arranged to emit a light beam along a simulation axis to simulate
ammunition from a weapon, coding means arranged to code the light beam
with information, and processing means arranged to calculate a trajectory
of simulated ammunition. The system is characterized in that the
processing means further are arranged to determine a point in time when
the simulated ammunition passes a target object and in that a control
unit is arranged to activate the transmitter for a predetermined time
period from said point in time and in that the control unit is arranged
to determine a value related to the distance between the simulation axis
and a momentary position of the simulated ammunition along the trajectory
at the determined point in time and in that said coding means are
arranged to code said light beam with the determined value.

[0025]Systems according to the present invention are, like U.S. Pat. No.
6,386,879, predicated on the target system itself assessing hit locations
based on information received from firing systems. The present invention
does enable this type of guidance, since the system is, as noted above,
based on the fact that it is primarily the firing system that calculates
and intermediates the ammunition trajectory. For example, weapons such as
the Javelin, with which the gunner can switch targets during the flight
of the ammunition by adjusting the trajectory with a joystick, can be
simulated in a realistic manner by using the invention. Further, the
system is suitable for both tactical training and firing range training.

[0026]In the absence of reflectors, the system according to the present
invention thus offers simplified installation and a substantially more
cost-effective system for larger targets. Installation on other targets,
such as vehicles and soldiers, is of course also simplified because
reflectors can be avoided. In terms of size, the detectors are generally
smaller and lighter than reflectors. The absence of reflectors means that
the detectors can be mounted with greater freedom, since they do not need
to be positioned in immediate proximity to a reflector. The invention
does however permit the presence of reflectors, as well as functionality
as per U.S. Pat. No. 4,218,834 in parallel with functionality as per the
present invention.

[0027]The fact that the transmitter is only activated during short time
period when the simulated ammunition passes a potential target object
decreases the power consumption of the transmitter substantially. Further
the risk of fighting more than the intended target decreases when the
light beam is only lit when the ammunition passes the target.

[0028]In one preferred embodiment of the invention the fire simulation
system comprises means for determining the position of at least one
target object and controllable steering means arranged to steer the
direction of the simulation axis toward the target.

[0029]In a preferred embodiment, the fire simulation system is arranged to
continuously update the geographical position, for example by means of a
satellite based positioning system such as GPS, of the weapon and of
potential targets within a target area for the weapon. In one example,
the geographical positions are updated with a first predetermined
frequency when a weapon simulation is not executing a simulation and with
a second, higher, frequency during fire simulation. The precise knowledge
of the positions of the weapon and target objects during simulation
provides for high accuracy in the simulations.

[0030]In order to further increase the precision of the simulation, the
weapon is provided with an orientation sensor arranged to sense the
aiming of the weapon. When the aiming of the weapon is known, it is
possible to define the target area for the weapon with high accuracy
using the aiming information and knowledge of the weapon.

[0031]According to one embodiment, the fire simulation system is either
partly or entirely disposed at the weapon.

[0032]Further embodiments of the fire simulation system are defined in the
dependent claims.

[0033]A weapon effect simulation according to one embodiment of the
invention comprises the fire simulation system described above and at
least one hit simulation system provided on each target object, said hit
simulation system including [0034]means arranged to receive the emitted
light beam and [0035]means arranged to determine whether the
corresponding target object has been hit based on the value coded in the
light beam.

[0036]In accordance with one embodiment at least one of the hit simulation
systems comprises a transmitter, and the fire simulation system comprises
a receiver arranged so as to receive information from the transmitter of
the hit simulation system. The transmitter of the hit simulation system
can be arranged so as to transmit a hit message upon determination of a
hit. Upon reception of a hit message, the control unit is in one
preferred embodiment of the invention arranged so as to break off the
simulation.

[0037]In yet another embodiment of the invention the means arranged to
determine hit are arranged so as to determine the hit location on the
target.

[0038]In summary, the system according to the invention and the method
according to the invention offer numerous advantages. First, the
ammunition can be simulated with great precision. The high precision is
achieved because hit points for the simulated ammunition are based solely
on the calculated trajectory of the real ammunition and knowledge of the
position of the target. No reflectors are needed in the target, since
information about the location of the target object in relation to the
light beam is derived from the information in the light beam. In
addition, the ammunition can be allowed to be guided or corrected after
firing, making it possible to simulate a larger number of weapon types
than before.

BRIEF DESCRIPTION OF FIGURES

[0039]FIG. 1 shows an example of an application of the invention for
firing practice.

[0040]FIG. 2 shows a block diagram of the simulation equipment contained
in the tank depicted in FIG. 1 according to one embodiment.

[0041]FIG. 3. shows the application in FIG. 1 with the imagined trajectory
of a simulated round of ammunition marked.

[0042]FIG. 4 shows a block diagram of equipment contained in a target
depicted in FIG. 1 according to one embodiment.

[0043]FIGS. 5 and 6 show schematically the concepts of the invention.

[0044]FIG. 7 shows a flow chart over a fire simulation method according to
one example of the invention.

PREFERRED EMBODIMENTS

[0045]A conventional weapon, which consists in the example according to
FIG. 1 of a gun on a tank 1, can be used as a weapon system in simulated
firing practice, wherein the weapon system 10 comprises the gun and a
simulation system disposed at the gun.

[0046]In FIG. 2, the simulation system comprises a transmitter device 2
disposed in connection with the gun, suitably in the barrel 4 of the gun,
and a simulator unit 3. The simulator unit 3 is connected with a firing
system 5 for the gun, an ammunition selector 18 for selecting the
ammunition type, a sensor arrangement 19 to determine, among other
things, the motion status of the weapon, and a GPS receiver 20 that
receives the geographical position of the simulator unit 3. According to
one embodiment, the GPS receiver is supplemented with a radio receiver
for receiving a correcting signal, so-called DGPS. The simulator unit 3
is also connected to a receiver 14, for example a radio receiver.

[0047]The weapon is aimed and fired as though a real round were being
fired, and each time the gunner fires the weapon, the simulator unit 3 is
activated. The simulator unit 3 contains a memory 22 arranged so as to
store an identity that is unique for the tank 1. Targets 10, 10' and 10''
also each have a unique identity stored in a memory 31 (FIG. 4) belonging
to each respective target. The tank 1 constantly receives geographical
position information via the GPS receiver 20. The targets 10, 10' and
10'' also possess knowledge regarding their current geographical
positions via a GPS receiver 32 disposed at each respective target.
According to one embodiment, the GPS receiver 32 is supplemented with a
radio receiver for receiving a correcting signal, so-called DGPS. Each
target is arranged so as to broadcast information about its position
together with information about its identity via a radio transmitter 26
and the receiver 14 of the weapon system is arranged to continuously
receive said information.

[0048]In FIG. 3, an imagined trajectory 16' of an ammunition 15 is
generated in that, upon firing of the weapon, a processing unit 17 that
works together with the control unit 6 is initiated to generate a signal
that reproduces the trajectory 16' of the ammunition 15, taking into
account such factors as will affect the trajectory before, after and at
the instant of firing. Factors that are of interest before firing include
the type of ammunition, which is selected in view of the target to be
attacked. In the illustrative example, the gunner indicates the selected
ammunition type by setting the ammunition selector 18, which is
operatively connected with the processing unit 17. Other factors that
affect the ammunition trajectory are the alignment of the weapon and its
motion status at the instant of firing. These parameters are supplied
from the sensor arrangement 19, which is operatively connected with the
processing unit. For example, the sensor arrangement 19 is equipped with
a gyro by means of which the motion status of the weapon is detected. The
influence of the atmosphere can affect the imagined ammunition trajectory
both stochastically and as calculated based on known conditions from
actual cases; such examples can include wind and air temperature. If the
imagined ammunition is of a type that is guided after firing, then the
guidance signals associated therewith are also included among the factors
that can affect the imagined ammunition trajectory. The processing unit
17 generates a signal that is determined relative to the gun and
represents the imagined ammunition trajectory 16.

[0049]The processing unit 17 is arranged to continuously determine a first
distance between the gun and each target 10, 10',10'' and to determine a
second distance between the gun and the momentary position of the
imagined ammunition along the trajectory in real time. In a simple
example, the first distance is calculated by comparing the geographical
positions received by GPS. In an extended example, the processing unit is
arranged to calculate the positions of the gun and targets based on the
GPS positions but also on measured accelerations etc and thereafter
calculate the first distance.

[0050]In one example, the processing unit 17 is arranged so as to
calculate the ammunition trajectory in real time, whereupon the most
recently calculated value is used for determinating the second distance.
Alternatively, the entire ammunition trajectory is calculated upon the
firing of a simulated round, whereupon the values at the calculation
points are output in real time in order to be used in determination of
the second distance. The processing unit 17 is arranged to continuously
monitor the first distance for each target to the second distance. When
the first and second distances coincide for one of the targets, that
target is selected. The processor unit 17 is then arranged to determine a
line of sight, or initial simulation axis based on the position of the
selected vehicle, known from the receiver 14, and the position of the
gun, known from the GPS-receiver 20. The processing unit 17 determines
the line of sight as a simulation axis and calculates the perpendicular
distance between the simulation axis and the momentary position of the
ammunition along the trajectory.

[0051]The information regarding the perpendicular distance is fed via the
control unit 6 to a code unit 21 in the transmitter device 2. In the code
unit 21, the information regarding the perpendicular distance is
converted into series of pulses and pauses by means of which the lobes 7'
and 7'' of the laser transmitter are modulated in a manner that is known
per se. The control unit 6 is further arranged so as to control a laser
transmitter 12 and a deflecting element 11 so that the coded laser lobes
7' and 7'' illuminate the target along the simulation axes during a
predetermined time period.

[0052]In an extended example, the laser lobes 7' and 7'' are caused to
rapidly and periodically scan an area at the selected vehicle during the
predetermined time interval. This is achieved in a known way via the
deflecting elements 11 that are arranged in the beam path of the laser
transmitter 12. The deflecting elements 11, realized in the form of e.g.
mutually movable optical wedges, are controlled by means of signals from
the control unit 6 so that each lobe executes a forward- and
backward-moving linear sweep movement with a predetermined speed and
direction of movement within a predetermined solid angle area whose
cross-section in FIG. 1. is designated 9', and which is suitably centered
relative to the barrel. However, the processing unit is arranged to
provide to the code unit a new distance value for the perpendicular
distance between the laser radiation and the momentary position of the
ammunition along the trajectory for each direction of the sweep. Thus, a
number of simulation axes are determined and a unique distance value is
calculated for each determined simulation axes.

[0053]In FIG. 4, a target system at each target 10, 10' and 10'' comprises
a receiver unit 27 comprising one or more laser radiation-sensitive
detectors 29 and a decoder 30. The fields of view of the detectors should
be such that radiation can be detected in all occurring directions of
fire as long as the target on which the detectors 29 are disposed is not
concealed. The information-bearing modulated radiation that is received
by the detectors 29 is converted into an electrical signal, which is fed
to the decoder 30 for conversion into a form that is suitable for
continued signal processing in a hit assessment unit 28. During the hit
assessment, a hit location for the ammunition is first calculated. In
this calculation, the orientation of the target is determined and a hit
point is determined based on the decoded distance, the hit location of
the laser radiation and the determined orientation of the target. The
orientation can be determined based on, e.g. the direction obtained from
the GPS receiver or knowledge as to which detectors have been
illuminated.

[0054]A vulnerability calculation is then performed to calculate the
effect that a real round of ammunition would have had on the target if it
had followed the same trajectory as the imagined ammunition. The
calculation is based on, e.g. a predefined division of the target into
different vulnerability fields, and translation of the above-calculated
hit point into a field number. A hit within a specified field yields a
specific effect, e.g. if a hit to the tank track results in a break in
the track, causing the tank to become immobile, the soldiers inside the
tank can continue to be combat-capable.

[0055]Based on the hit assessment, the hit assessment unit 28 generates a
message and supplies that message to the radio transmitter 26, which
transmits the message. The message can include, e.g. information about
the identity of the target, the identity of the weapon that caused the
damage, the ammunition type/ammunition identity, and the degree of damage
inflicted on the target. During use in a military exercise, the message
is received by a central unit that receives status messages from all the
actors involved in the exercise that have a separate identity, such as
people, weapons, vehicles, etc. In one example the radio receiver 14 of
the tank is arranged so as to receive the status messages, and the
control unit 6 is arranged so as to break off the simulation of the
ammunition 15 upon receiving a message that the ammunition 15 has hit. As
previously described, the target system also contains a GPS receiver 25
operatively connected to the transmitter 26 arranged to broadcast
position data for the target.

[0056]FIG. 5 shows the weapon system 33 in relation to a number of
potential targets. Only targets A, B and C are within the target area 8
for the weapon and thus only targets A, B and C can be affected by the
simulation. The target area 8 can be determined by the GPS-positions of
the weapon and potential targets and data from an orientation sensor of
the sensor arrangement 19 of the weapon, said orientation sensor
describing the aiming of the weapon. The orientation sensor is for
example a compass of some kind, such as a magnetic, north seeking gyro or
a double GPS. The size of the target area 8 is determined by the accuracy
of the GPS information, the performance of the orientation sensor and the
updating frequency of the position information for the weapon and
potential targets. The sweeping area defined by the lobe 9 is much
narrower than the target area. When the simulated ammunition reaches the
distance A the transmitter device is arranged to perform the sweeping
movement within the lobe 9 and directed towards the target A. When the
simulated ammunition reaches the distance for B, the transmitter device
is arranged to perform the sweeping movement within the lobe 9 and
directed towards the target B. When the simulated ammunition reaches the
distance for C, the transmitter device is arranged to perform the
sweeping movement within the lobe 9 and directed towards the target C.
The sweeping area defined by the lobe 9 is dependent on the size of the
targets in relation to the number of detectors mounted on the targets.
For example, for a huge target having detectors on only small region(s)
thereof, a broad sweeping lobe 9 is required in order to secure that the
laser radiation hit the detector(s). On the other hand for a small target
covered with detectors only one laser beam is required.

[0057]In FIG. 6, axes 23 depicts a first simulation axis in the sweep and
axes 24 depicts a second simulation axis in the sweep. It is to be
understood that this example is for illustrative purposes only. In
reality, the sweep contains a large number of simulation axes. For each
simulation axes, the laser radiation is coded with a distance value
indicating the perpendicular distance to the momentary position of the
ammunition 13 along its trajectory. The laser beam along axes 23 is coded
with the distance value d1 while the laser beam along axes 24 is
coded with the distance value d2. The distance values d1,
d2 are to be understood to include information regarding both the
distance to the ammunition and the direction to the ammunition.

[0058]In the example of FIG. 6, the laser radiation transmitted along the
axis 24 reaches the target. The target is then arranged to perform hit
evaluation, as described above, based on the information coded in the
laser beam and a target template 25.

[0059]In FIG. 7, fire simulation simulating fire from a weapon starts when
the firing system 5 is triggered. In a first step 34 a trajectory of the
simulated ammunition is determined. In a second step 35, the target area
8 is determined. The target area is for example determined based on
aiming information from an orientation sensor on the weapon and based on
information regarding the range of the weapon for example stored in the
memory 22. In a third step 36, the geographical positions of the weapon
and targets are inputted. The inputted geographical positions are used in
a fourth step 37 to determine a distance between the weapon and each
target present within the target area. In a fifth step 38, the distances
calculated in the fourth step 37 are compared to a distance to the
momentary position of the ammunition along its trajectory. If one of the
targets have been passed, i.e. if the distance to the momentary
ammunition position exceeds one of the target distances, the simulation
proceeds in a sixth step 39 for that selected target. If no target still
has been passed, the simulation goes back to the second step 35 in the
shown example. In an application where the targets are expected to be
moving slowly, the process can go back to the third step 36 instead, and
in an application where the targets are expected to be moving even more
slowly or be stationary, the simulation process can go back to the fourth
step 38. A delay time can be set before the simulation goes back to the
second, third or fourth step.

[0060]In the sixth step 39, a simulation axis i is determined such that a
light beam transmitted along said simulation axis is directed toward the
selected target, and a distance value di is determined describing
the perpendicular distance between the simulation axis i and the
momentary ammunition position. In a seventh step 40, a light beam is
emitted along the simulation axis i and coded with at least the distance
value di. The light beam is arranged to perform a predefined sweep
around an initial simulation axis 0. If the sweep is not completed, a new
simulation axis i+1 is determined in accordance with predefined criteria
in an eight step 41 and the sixth and seventh steps 39, 40 are repeated
until the sweep is completed. In an alternative example, the simulation
axises of the whole sweep and corresponding distance values are first
determined, and then the determined data is used for deflecting the light
beam and coding the light beam in the manner described above.

[0061]When a sweep is completed it is determined whether the simulation is
to be ended. The simulation is ended for example if an hit message is
received or if the ammunition is determined to have hit ground (reached
the end of the trajectoria) or if all targets have been passed. If the
simulation is not to be ended, the process goes back to the second step
35 but the previously selected target is removed from the simulation.